This invention concerns a valve assembly and connection of two valve assemblies. More particularly, the valve assembly concerns shut-off of a liquid flow in such a manner that subsequent draining is avoided, and that two components having each a valve assembly according to the invention may be separated using little force, and without reducing the system pressure.
In order to shut off a fluid flow in a conduit, it is known to use a valve. A number of types of valves are known in the field. A group of valves is known as quarter-turn valves and comprise, for example, ball valves, butterfly valves and plug valve. The characteristic of a ball valve is that the valve element is ball-shaped. The valve element, hereinafter termed the ball, has a through opening. When the opening of the ball is in-line with the longitudinal direction of the valve, the direction of which is defined as the direction between the centre of the inlet opening and the centre of the outlet opening, fluid flows through the valve. When the opening of the ball is perpendicular to the longitudinal direction of the valve, the valve is closed. A ball valve has a simple packer arrangement. One packer lies fiat and sealingly against the ball at the side facing the inlet of the valve, and one packer lies flat and sealingly against the ball at the side facing the outlet of the valve. This prevents the fluid from penetrating between the surface of the ball and the internal mantel of the valve housing. Such a leakage is undesirable.
A plug valve is comprised of a cylindrical plug or a plug tapering off into a frustum shape. A plug valve may be provided with one through opening or it may be provided with several through openings, or it may be a so-called 3-way valve having several channels within the plug. Such plug valves are known from, for example, laboratory equipment and may be made from glass. The formed annulus between the surface of the plug and the valve housing may be filled with a lubricant in order for the plug to be rotatable.
In the field of underwater technology, it has for a long time been customary to transfer hydraulic energy from, for example, an underwater vessel, oftentimes denoted as a ROV (Remote Operated Vehicle), by means of a connection mandrel, also termed a hot stab in the field. The hot stab may be displaced into a connection block belonging to to a fixed underwater installation or belonging to a temporarily placed piece of equipment or tool. The connection block has a through opening for the hot stab. This ensures that the nose of the hot stab does not abut a surface and becomes damaged. A ROV has a considerable weight, it is remote-controlled, and currents in the water may allow a ROV and its equipment to collide with a considerable force into other structures.
The hot stab may be, and usually is, provided with several conduits for various fluid circuits. Channels in the hot stab fit in a complementary manner into corresponding channels in the connection block when the hot stab is located in its operational position in the connection block. Such hot stabs are, to a large extent, standardized and well-known to a skilled person.
During connection or disconnection of the hot stab with respect to the connection block, the fluid circuits must be shut off, whereby the connection/disconnection may take place without having to overcome the pressure-forces of the fluid. Even though the hot stab is pressure-balanced during shut-off, the pressurization will increase the packer friction, whereby especially a disconnection must overcome this packer friction. Shut-off of the fluid circuits take place via use of isolation valves in the fluid channels leading onto the connection block, and in isolation valves in the fluid channels leading onto the hot stab.
It is not desirable for the fluid to drain out from the connection during connection operations or disconnection operations, and this is subject to strict statutory requirements. In order to reduce a discharge as much as possible, valves are placed as close as possible to the mouth portion of the fluid circuits. Within the hot stab, it is known to place directly pilot-controlled check valves in the mouth portion of the fluid conduits. However, the known check valves are not completely impervious, nor can they withstand a full system pressure.
In many cases, it is not possible to replace the connection block and, in some areas of application, and for safety reasons, a double set of isolation valves are therefore required for each fluid conduit. A connection block having three fluid conduits may thus be provided with 3 to 6 valves with associated apparatuses in order to control them, depending on statutory requirements and/or system requirements.
Patent publication WO 89/03002 describes a coupling connection for offshore use in the petroleum industry. The coupling connection consists of a male member and a female member. The wall of the female member forms a circular cavity, and the wall is provided with radial bores for a fluid. The bottom portion of the cavity is provided with o a coupling mechanism. At the side facing the cavity of the female member, the wall is provided with a rotatable first sleeve, hereinafter termed the female sleeve. The female sleeve forms a rotatable closing element. The female sleeve, at the inside thereof, is sloping slightly having the largest diameter in a portion facing the open end of the female member, and having the smallest diameter in a portion facing the bottom portion of the cavity. The female sleeve is provided with radial bores. In an open position, the radial bores of the wall will correspond to the radial bores in the female sleeve. When the female sleeve is rotated into a closed position, the radial bores of the wall will terminate against an impervious portion in the female sleeve. A packer arrangement having two concentrically arranged packers concentrically surrounding the radial bore, and a further droplet-shaped packer which will surround both the bore in the wall and the bore in the female sleeve when the female sleeve is in a closed position, is also described. By so doing, a fluid will not be able to penetrate into the annulus formed between the wall and the female sleeve. The male member fits in a complementary manner to the female member. The male member is comprised of a mandrel which, in one end portion thereof, is provided with a coupling mechanism structured on as to be temporarily lockable to a locking mechanism of the female member. In its mantel, the male member is provided with radial bores connected to the channels in the mandrel. In a portion, the channels extend axially within the mandrel. A portion of the mandrel of the male member, the portion of which is located proximal to the locking mechanism of the male member, is surrounded by a rotatable second sleeve, hereinafter termed the male sleeve. The male sleeve is provided with radial bores. In principle, the male sleeve cooperates with the mandrel in the same manner as the female sleeve cooperates with the wail of the female sleeve and may be in an open position and a closed position. Between the mandrel and the male sleeve, the male member is provided with the same packer arrangement as described above. By so doing, a fluid will not be able to penetrate into the annulus formed between the mandrel and the male sleeve. The male sleeve, at the outside thereof, is tapering slightly having the smallest diameter proximal to the locking mechanism of the male member. When the locking mechanism of the male member is engaged with the locking mechanism of the female member, the outside of the male sleeve will fit in a complementary manner to the inside of the female sleeve. The coupling connection is equipped with a guide, whereby the radial bores of the female sleeve correspond to the radial bores of the male sleeve. The coupling connection is further provided with ring-shaped packer elements sealing between the radial bores of the female sleeve and the male sleeve. After connection of the coupling connection, the fluid communication between the female member and the male member is opened upon simultaneously rotating the female sleeve and the male sleeve from a closed position to an open position. Disconnection takes place by rotating, at first, the female sleeve and the male sleeve from an open position to a closed position, and then activating the locking mechanism, whereby the male member may be pulled out of the female member.